Kallmann Syndrome is a hereditary condition characterized by anosmia (the inability to smell) and hypogonadotropic hypogonadism resulting in infertility. This disorder affects 1 in 10,000 males and 1 in 40,000 females, but may be under diagnosed due to mild cases of hypogonadism or hyposmia. To date, five genes associated with KS have been identified, namely, KAL1, FGFR1, FGF8, PROKR2, and PROK2; though these only account for approximately 30% of all KS cases. The goal of this project is to identify and characterize novel genes that genetically interact with kal-1, a gene that codes for a cell adhesion protein of the extracellular matrix. We propose to accomplish this using a modifier screen of a kal-1 gain of function axon branching phenotype in C. elegans. A pilot screen of this phenotype has been used successfully by our group to identify several novel loci that genetically interact with KAL-1, both in worms and humans. The newly isolated mutations will be molecularly identified through single nucleotide polymorphism mapping and whole genome sequencing approaches. RNAi mediated knock down experiments and transgenic rescue experiments will be performed to further corroborate the identity of the mutation. The identified genes will then be molecularly and genetically characterized by three complementary approaches to gain a deeper understanding of how kal-1 acts in concert with these genes on the development of the nervous system and the role of the extracellular matrix in this process. First, I will perform a detailed neuroanatomical and phenotypic analysis of the modifier mutants with a focus on the nervous system. Second, their site of expression and the sub cellular localization will be determined, which will give important clues to the function of the protein. Third, double mutant and epistasis analyses will be performed in order to place the new mutations within a known genetic context. In the end, as more genes that interact with KAL-1 are identified, we will have a better understanding of their function and how their disruption in humans results in Kallmann Syndrome.